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New Look at Vietnam Vets' PTSD Data

August 17, 2006

A report published Friday in the journal Science has found "very little evidence of falsification" by Vietnam veterans with Post-Traumatic Stress Disorder. The researchers selected a sample of 260 participants from the 1988 National Vietnam Veterans Readjustment Study (based on data from surveys of 1,200 veterans) and used military records to verify traumatic events reported by the veterans.

The authors of the new study also found rates of PTSD that differed from the NVVRS estimates. The NVVRS found that 15.2 percent of veterans had PTSD at the time of the study; 30.9 had PTSD at some point during their lifetime. The new analysis finds 9.1 percent with a "current" diagnosis and 18.7 percent with a "lifetime" diagnosis.

Dr. Matthew J. Friedman, executive director of the National Center for Post-Traumatic Stress Disorder for the Department of Veterans Affairs (and a member of the Dart Center advisory council), told New York Times reporter Benedict Carey that "We can quibble about the numbers but the point is that it’s a lot of people." Harvard psychologist Richard McNally--a long-time and outspoken critic of the NVVRS estimates--said that the new numbers "should not be used as a justification for short-changing services that are needed to help veterans." (Click here for an NPR report about the new study.)

UPDATE (Friday, 11:30 am): The study (subscription required) goes a long way toward refuting critics who claim that the NVVRS PTSD-prevalence estimates are inflated by the fraudulent claims of benefit-seeking veterans. Using military records, military histories and newspaper accounts, the authors report that they were able to confirm "the exposure to traumatic stressors of most of the subsample veterans."

The authors also examined the "conundrum" frequently cited by critics of the NVVRS: only 15 percent of troops in Vietnam were classified as having "combat exposure" but 30.9 percent eventually had PTSD. The authors were able to establish that "non-combat" soldiers in Vietnam were, in fact, exposed to significant, verifiable stressors. The authors found a strong relationship (stronger than was identified by the NVVRS, in fact) between PTSD symptoms and exposure to war-zone stressors, which the authors note is a "relationship that cannot be due to biases in self-reports of exposure."

The authors also address the disparity between the PTSD prevalence figures of the NVVRS and those of the Centers for Disease Control study, which "reported rates of 14.7% lifetime PTSD and 2.2% current PTSD 11 to 12 years after the Vietnam war ended." This disparity, the authors say, is not due to flaws in the NVVRS (as critics have contended) but because the CDC used a partial version of a survey that has since been found to underestimate PTSD. The authors explain:

The CDC used about half of the items from a newly developed module from the Diagnostic Interview Schedule (DIS) to diagnose lifetime and current PTSD on the basis of responses to closed questions asked by lay interviewers. This version of the DIS PTSD module has been found to diagnose much lower rates of PTSD in the general population than the other diagnostic instrument that is most widely used by lay interviewers. Against this background, it is not surprising that the abbreviated CDC adaptation of the DIS PTSD module was found in the NVVRS to miss 78% of veterans who had diagnosable PTSD, according to the SCID clinicians. These results suggest that PTSD is under-diagnosed in both military and civilian samples when this version of DIS PTSD is used.

The authors conclude:

The message from the NVVRS has been that the Vietnam War took a severe psychological toll on U.S. veterans. Our results provide compelling reasons to take this message seriously.

UPDATE 2 (Friday, 3:00 pm): Why are the rates of PTSD in this new study lower than the NVVRS rates?

Seven veterans with PTSD were removed from the sample group: "four veterans with prewar onset, two missing onset information, and one missing sampling weight." Once these seven were removed from the analysis, "unadjusted" rates of PTSD were found (22.5 percent "lifetime"; 12.2 percent "current"). Then, these rates were adjusted for "impairment of functioning" (the current criteria require that symptoms cause a certain level of impairment before PTSD can be diagnosed; the criteria in place at the time of the NVVRS did not) and "documentation of exposure" (eight veterans in the sample group with PTSD reported stressors that could not be confirmed by independent sources; of these eight, the authors write, "Record information was contradictory for only two").

One point likely to be noted by critics of this study is the exclusion of veterans with prewar onset of PTSD. A prewar diagnosis doesn't necessarily invalidate a war-time stressor. The authors do not reveal whether those veterans' re-experiencing symptoms (nightmares, flashbacks) are of the prewar trauma, or of the war-zone trauma. If the nightmares and flashbacks of a veteran with a prewar diagnosis were mainly of war-time stressors, it would be hard to say that veteran's PTSD was not "war-related."